Electronic musical apparatus

ABSTRACT

An electronic musical instrument in which the fingerboard of a guitar is replaced by capacitive touch contact switches simulating all of the fret positions of a string. The touch plates are coupled to various oscillators and the output frequency is amplitude modulated by a transducer produced output signal from a set of strings which are plucked. This output signal is stretched and shaped as desired to modulate the audio frequency signal and produce the final musical output.

United States Patent Allen et al. 1 May 16, 1972 [54] ELECTRONIC MUSICALAPPARATUS 3,165,022 1/1965 Yokoyama ..84/1.l4 [72] Inventors: JosephStevens Allen, 202 Valparaiso, g i Atherton, Calif. 94025; Zeb VanceBulla, y

Jr., 4018 C Woodmont, Nashville, Tenn. O H PUBLICATIONS 37205Electronics World, Vol. 65, N0. l,Jan. 1961, pp. 29- 32; 125, [22]Ftled: Octl, 1 70 A Transistorized Teremin," [2]] Appl' 77280 PrimaryExaminer-J. D. Miller Rehted us Application Data Assistant Examiner-R.Skudy Attorney-Flehr, Hohbach, Test, Albntton & Herbert [63]Continuation-impart of Ser. No. 864,024, Oct. 6,

1969. [57] ABSTRACT 52 us. 01 ..s4/1.o1, 84/].16, 84/1.l7 P musicalwhich the fingerbwfd of [51] Int. Cl. ..G01h 1/00 a replaced by capacmvetouch Contact swnches [58]" Fie'd of Search 84/101 1,14 1,16 1.17 Plating all of the fret positions of a string. The touch plates are 334/1coupled to various oscillators and the output frequency is amplitudemodulated by a transducer produced output signal from a set of stringswhich are plucked. This output signal is [56] References Cned stretchedand shaped as desired to modulate the audio UNITED STATES PATENTSfrequency signal and produce the final musical output 3,493,669 2/1970Elbrecht ..84/ l 16 32 Claims, 8 Drawing Figures TO I OTHER 5&8 66

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ATTORNEYS 'PITE'N'TEDMAY 161m 3.662.641

sum 3 P 4 FROM TRANSDUCER LL] 0 Z ,3 BALANCED OX2 g REACTANCE 3tMODULATOR U I CXI cxo UN|TY o +UN|TY out in out oui in BALANCE CONDITIONINVENTORS F G 4 J. STEVENS ALLEN BY ZEB VANCE BULLA,JR.

M W, (m f M ATTORNEYS ELECTRONIC MUSICAL APPARATUS CROSS-REFERENCE TORELATED APPLICATION This application is a continuation-in-part ofcopending application, Ser. No. 864,024, filed Oct. 6, 1969, in thenames of J Stevens Allen and Zeb Vance Bulla.

BACKGROUND OF THE INVENTION The present invention is directed in generalto an electronic musical apparatus and more particularly to musicalapparatus of the stringed type.

With the advent of solid state electronics the use of electronicamplification for stringed instruments has been widespread. Thisamplification has also included echo or reverberation effectsaccomplished by introducing a time delay in one channel ofamplification.

The present invention is directed in general to an electronic musicalapparatus and more particularly to musical apparatus of the stringedtype.

With the advent of solid state electronics the use of electronicamplification for stringed instruments has been widespread. Thisamplification has also included echo or reverberation effectsaccomplished by introducing a time delay in one channel ofamplification.

However, except for the elimination of an acoustic sounding box,stringed instruments such as the guitar have been essentially unchangedin their basic construction. In other words, present amplifiedinstruments have not provided a design in the music producing andamplification portions which have been truly integrated.

It is, therefore, a general object of the invention to provide animproved electronic musical apparatus in which the electronic portion isintegrated with the music producing portion of the apparatus.

It is another object of the invention to provide apparatus as abovewhich produces novel musical sounds and effects and greatly increasesthe versatility of standard stringed instruments when modified inaccordance with the invention.

In accordance with the above objects there is provided electricalmusical apparatus comprising transducer means adapted for actuation by ahuman hand. A plurality of touch actuated switch means are provided eachcorresponding to a predetermined audio frequency signal. Oscillatormeans are coupled to the switch means and are responsive to theselective actuation of any one of the switch means for generating anaudio frequency signal corresponding to the switch means which has beenactuated. Modulating means are coupled to the oscillator means andtransducer means are responsive to the actuation of the transducer meansconcurrently with the actuation of one switch means for modulating theaudio frequency signal.

FIG. I is a schematic representation of a musical instrument embodyingthe present invention along with a schematic block diagram illustratingthe associated electronic portion of the invention;

FIG. 2 is a detailed circuit schematic of a portion of FIG. 1;

FIG. 3 is a detailed circuit schematic of another portion of FIG. 1;

FIG. 4 is a circuit characteristic useful in understanding the presentinvention;

FIG. 5 is a block diagram showing a modification of the circuit ofFlG.1;

FIG. 6 is a block diagram showing another modification of the circuit ofFIG. 1;

FIG. 7 is a block diagram illustrating a modification of the outputcircuit of FIG. 1;

FIG. 7A is a detailed schematic of a block of FIG. 7; and

FIG. 8 is a cross-sectional view of a modification of the stringingarrangement of FIG. 1.

Referring first to FIG. 1, the present invention is shown in itspreferred embodiment as a guitar 10 which, as will be explained indetail below, has been modified in accordance with the principles of thepresent invention. However, it should be understood that the presentinvention is applicable to any stringed instrument. Guitar 10 includestypical portions such as a neck 11 with a fingerboard 12, a head 13having tuning machines 14a-f and a table portion 16 having stretchstrings 17a-f mounted around rubber studs 18 by springs 19. The stringsare arranged so they may be plucked by fingers or a plectrum. Stringsl7a-f do not extend over the fingerboard to the tuning machines 14a-f.Instead they are short and lie only on the table 16.

The displacement of the strings is picked up by two sets ofpiezoelectric transducers 21 and 22. The individual transducers areconstructed similarly to photograph pickups. Transducer set 21physically contacts strings 17 slightly in front of studs 18 to causethem to be primarily responsive to transverse mode vibrations of thestrings. Transducer set 22 contacts portions of strings 17 which arewrapped around studs 18 and are thus primarily responsive tolongitudinal mode vibrations.

As will be clearly apparent, the frequency of the musical signal is notdependent upon the strings; rather only the amplitude and partially therise and fall duration of the musical sound is determined by the strings17a-f. Moreover, by controlling the location at which the strings areplucked, the longitudinal or transverse modes can be emphasized toachieve special sound effects. For example, plucking near the transversemode transducer 21 will produce a twanging effect.

Fingerboard 12 instead of having strings and being fretted to produce avariation in musical pitch consists of columns of touch plates 26a-f inthe form of wire segments which correspond to or simulate the stringswhich would otherwise be in those column locations. In addition, each ofthe simulated string columns 26a-f correspond to the tuning machinesl4a-f and may in fact be tuned in the same manner as a typical stringedguitar. More specifically, each touch wire column 26a-f is arranged in astraight line and each touch wire designated 27 simulates a specificfingering position of a string in the same physical location. Thus, thespacing and configuration of the touch wire 27 would be varied dependingupon the type of stringed'instrument being simulated. For example, witha classical guitar the touch wires 27 would be spaced farther apartbecause of the wider neck of that guitar as opposed to a folk" typeguitar with a narrower neck.

Each touch wire 27 is coupled to an individual switch 28 which isactivated when a finger of the player is placed on the wire. This actionplaces a virtual capacitor in the associated circuitry in a well-knownmanner. FIG. 1 shows switches 28 coupled to only touch wire column 26f.However, all touch wires would be connected to their own touch sensitiveswitches.

Each column 26a-f of touch wires 27 and their associated touch-actuatedswitches 28 are associated with an oscillator 29. As shown in FIG. 1 thesubscript of the oscillator 29f corresponds to the simulated string;namely 26f. Touch actuated switches 28 are coupled to oscillator 29fthrough a series of resistors 31f which includes a V voltage supply onone end. V is provided by a radio frequency oscillator 30 having aninput power source +V coupled through a resistor 33. The output R.F.signal modulates a +V voltage supply which is a.c. isolated by a chokecoil 34.

Oscillator 29f is also coupled to a corresponding tuning machine 14fwhich includes a variable resistor 32f which, as will be explained indetail below, controls the basic frequency of oscillation of oscillator29f. The remaining tuning machines l4a-f would be coupled to theirrespective oscillators 29a-e (not shown). All of the oscillators 29a-fare respectively coupled to an isolation amplifier 35a-f which preventsthe loading of the associated oscillators 29a-f by the subsequentcircuits. Amplifier 35f is coupled into a balanced modulator 36f throughseries resistors 37f and 38]". The balanced modulator is of a typecommercially available as a unit and produces no output in the absenceof a modulating input on line 39f.

Harmonic control means are coupled between resistors 37f and 38f andinclude a balanced reactance modulator 41f having a capacitor 42f acrossits signal input, V,,,, and output terminals, V 43f and 44f and a thirdmodulation input terminal 46f coupled to a potentiometer 47f. Outputterminal 44f is coupled between resistors 37f and 38f.

Potentiometer 47f provides either a null or zero input or is variablebetween +V and V voltage as indicated. Such inputs when applied tomodulating input control terminal 46f varies the gain of the modulator41f and in turn the value of capacitor 42f is illustrated in FIG. 4. At0 voltage gain dB) where V,,,,,--0 the true value of the capacitor (CX 1) is in the circuit; at unity gain inverted where V V,,, theeffective value is doubled (C X 2); and at unity gain not inverted whereV V the value is zero (C X 0).

Harmonic control is effected by variation in the effective value ofcapacitor 42f which smooths or integrates the triangular waveform outputof oscillator 29 by attenuating its higher harmonics.

The audio signal from oscillator 29f and modulator 36f is coupledthrough and modulated by a series connected balanced modulator 51fhaving a modulation input 52f. The series cascading of the modulatorsforms a combined modulation characteristic which is logarithmic. Sincethe response of the human ear to sound is non-linear a logarithmiccharacteristic partially compensates for this nonlinearity. The abovecombination also produces a better null than a signal modula- I01. 1

Both modulators 36a-f and Sla-f are respectively responsive to thebowing or plucking of string means 17a-f to modulate the audio frequencysignals from the oscillators 29a-f in accordance with the displacementof the strings l7a-f. Specifically, modulator 36f is responsive tosignals from transducer set 21 which are coupled to its modulation input39f through a stretching and shaping unit 53f. This unit modifies theoutput of transducer set 21 by stretching the output waveform, theamount of stretching being varied by a control 54f, and delaying theproduction of the signal by means of a delay attack control 56f.

Similarly, input 52f of modulator 51f is coupled to transducer set 22through a stretching and shaping unit 57f having stretch and delaycontrol 58f and 59f.

The final modulated outputs of all balanced modulators Sla-fare coupledto an amplifier 60 and speaker 61.

Means for muting the audio output of the apparatus is provided by theassociated circuitry of R.F. oscillator 30. A capacitor 62 coupled tothe +V power input of the oscillator is responsive to the change inpower requirements when the touch activated switches are deactivated.The resultant change in stored charge is coupled through a conductor 63to stretching and shaping circuits 53a-f, 57a-f causing these circuitsin turn to disable the modulators 36af, Slain other words, zeromodulation is produced on inputs 39a-f and 52a-f. Details of the mutingcircuit are shown in FIG. 3.

Several alternative schemes are also available for muting. For example,a threshold circuit may be placed in line 63 so that muting will occuronly if a predetermined number of switches 28 are deactivated. For amore complete control arrangement each simulated string column 26a-f mayhave a separate R.F. oscillator 30 with individual muting controls.

Simultaneous tuning of all simulated strings (or a simulated capo) isachieved in the present invention by connecting variable resistors32a-fto a common junction 66 and varying the voltage level of thejunction. This simultaneously shifts the frequencies of oscillators29a-f by a common amount. An option switch 67 coupled to junction 66 toeither a foot pedal operated continuous potentiometer 68 or a detentedpotentiometer 69. Foot pedal 68 may, of course, be detented if desired.

Special effects can be achieved by feeding an a'.c. signal to thejunction 68 in effect modulate the tuning voltage. Also either or bothtuning potentiometers may be ganged with other electronic musicalapparatus embodying the present invention to in effect allow an entireband to easily tune to various musical keys.

in operation, the electronic musical apparatus of the present inventionis initially tuned by varying the knobs on tuning machines l4a-f.Oscillators 29a-f, in effect, produce the fundamental mode frequencieswhich would be produced by unfretted strings. Movement of the finger upthe fingerboard 12 along a given column of touch segments 27 graduallycuts out resistors of resistor string 31 to increase the frequency ofoscillation of oscillator 29 in the same manner and proportion as anactual string which is fretted. More specifically, for example, theoscillator 29 vibrates at the fundamental frequency of the string whichit represents and then as the touch segments 27 are activated it willincrease in frequency in accordance with the touch segment correspondingto that fret position.

The use of simulated tuning machines 14a-f and touch wire columns 26ainthe same location as they would be for an actual stringed guitar, makesadaptation to the electronic musical apparatus of the present inventionextremely easy for the experiencedplayer of an actual stringedinstrument.

The specific audio frequency signal or combination of frequency signalswhich are applied to the modulators 39 and 51 by oscillators 29a-f aremodulated by the displacement of the strings 17a-f. This displacement isrepresented as an electrical waveform which can be stretched in time bymeans of stretching adjustments 54, 58 or the delay attack controls 56,59 to achieve special effects. The outputs of stretching and shapingcircuits 53f and 57f are also coupled to the input terminal 46 ofbalanced re'actance modulator 41 to cause the harmonic content of theaudio output to vary in accordance with the modulation signal.

FIG. 2 shows greater details of a touch-sensitive switch 28 along withoscillator 29f. The capacitance produced when the finger touches thetouch plate 27 is shown by a virtual capacitor 70. This capacitor iscoupled into the switch 28 between diodes 71 and 72 through a dc.blocking capacitor 73 which guards against shocks to the player of theapparatus and also protects the diodes and transistors againstaccidental grounding. Diode 72 is coupled to the base of a transistor Q1and diode 71 to the emitter of Q1. The emitter of O1 is also coupledthrough a dc. blocking capacitor 74 to the radio frequency oscillator30. This may be of a frequency of from 1 to 75 megahertz and providesfor operation of the touch-sensitive switch in a manner well-known inthe art. The collector of O1 is coupled to a resistor string 31f coupledin turn to oscillator 29f; more specifically to the emitter of anunijunction transistor 02.

A capacitor 76 is also coupled to the emitter of Q2 and provides thebasic free-running frequency of the oscillator. One of the inputterminals of O2 is grounded and the other connected between seriesconnected resistors 77 and 78. These resistors are also coupled to therespective tuning machine resistors 32af (in this case 32f) to vary thebiasing of O2 to determine the oscillation frequency of oscillator 29fin combination with capacitor 76. More specifically, the discharge pointof capacitor 76 is determined by Q2 and its charging rate is determinedby the number of resistors in resistor string 31f The fewer in number ofresistors the faster the charging rate; therefore, the higher thefrequency the higher the pitch. Oscillator 29 because of the aboveconstruction produces a sawtooth type output. In addition, the use of aunijunction type transistor allows the frequency of oscillation to belinearly varied with the above change in resistance.

The output of oscillator 29f is coupled to an isolation amplifier in theform of a field effect transistor whose purpose is to prevent theloading of the oscillator by the subsequent balanced modulators.

A typical stretching and shaping circuit is shown in greater detail inFIG. 3. The output from transducers 21 or.22 is coupled into atransistor Q3 which is coupled to waveshaping circuits which include apotentiometer 81 and a switch 82 which may be switched between threecapacitors 83, 84 and 85. The potentiometer and switch may be joinedtogether as shown by the dashed line 46 which will in effect be thestretch switches 54, 58 of FIG. 1. The output of waveshaping circuit 81,82 is coupled into the base input of a transistor Q4. The emitter outputof Q4 is coupled to a switch 86 which also includes three capacitors toprovide for delay of the signal which is then coupled to balancedmodulators 36, 51.

The shaping circuit of FIG. 3 may be elaborated on and modifiedextensively. For example, resonant circuits and feedback circuits may beused when desired.

In order to achieve a greater degree of harmonic control of the outputof oscillator 29, a variable symmetry chopper circuit may be used inplace of balanced modulator 41f and capacitor 42f. Such a modificationof the circuit of FIG. 1 is illustrated in FIG. 5 where the output of anisolation amplifier 35f, which is in the form of a triangular waveshape101, is coupled to a variable symmetry chopper 102]. This chopper isdriven by the oscillator 29f and produces a pulse type output 102 on anoutput line 103 whichis coupled to balanced modu-' lator 36f.

Chopper l02f is actually in the form of a saturated differentialamplifier and includes transistors 104 and 105 having their emitterscoupled together and to a negative voltage source and their collectorscoupled through resistors to a common positive voltage source. A Schmitttrigger circuit may alternatively be used. However, the base input oftransistor 105 is coupled to potentiometer 47f along with the outputs ofstretching and shaping circuit 52f and 53f to vary the point on thewaveshape 101 at which the chopper clips. This causes a variation in thesymmetry of the pulse train 102 as illustrated by the dashed outline107. In other words, the actual pulse width of pulse train 102 is variedin accordance with the control input voltage on the base of transistor105 to provide pulses of variable width.

In accordance with well known Fourier analysis a change in width willchange the harmonic content of the pulse train 102 with a greater widthproducing lower harmonics and the narrower width producing a higherratio of upper harmonics. Thus, by variation of the pulse width theharmonic content of various stringed instruments can be approximated.Moreover, since the control input to the base of transistor 105 is alsocoupled to the output of the stretching and shaping circuits 52f and 53fa variable harmonic content can be produced during the plucking of asingle string. This can produce, for example, a familiar twanging sound.

Another variation in circuitry which allows the user of the musicalapparatus to supply a tremolo or vibrato is illustrated in FIG. 6. Herethe RF oscillator 30 is shown with its input current being supplied froma positive voltage source through resistor 33. Variation of the skinpressure produced by the finger on one of the touch plates 27 shown inFIG. 1 causes a change in the input current of the RF oscillator and thevoltage on resistor 33. Further in accordance with the invention acontrol unit 110 along with a sensitivity control 111 is coupled toresistor 33 and to the line 66 which controls the tuning of the musicalapparatus of the present invention. As discussed previously, the tuningcontrols modify the frequency of oscillation of the oscillators 2911-Since control unit 110 feeds back a portion of the voltage acrossresistor 33, variation of this voltage will also cause a concommitantchange in the tuning voltage to thus produce the desired vibrato effectin response to a variation of the skin pressure on the touch plates. Theamount of tremolo or vibrato is controlled by sensitivity control 111. I

Similarly, control unit 110 may be coupled to choppers 102a-f and tostretching and shaping circuits 53a-f, 57a-f to provide for specialeffects modulation.

Further control of the audio output of the musical apparatus of thepresent invention is provided by the use of a filtering circuit at theoutput of amplifier 60 and the input of loudspeaker 61. Filtering means112, as illustrated in FIG. 7, includes four filter componentsdesignated 112a through 112d each having a richness control 113 andtimbre control 114. The richness controls in the preferred embodimentare ganged together. FIG. 7A shows a typical filter 112a which includesa plurality of 'rr sections each having an inductor and two capacitors.The timbre control 114 ties to ground the capacitors of two 1r sectionsand bridges across the inductors of these 1r sections to provide inputand output terminals which are respectively coupled to the amplifier 60and loudspeaker 61. However, the input terminal has series connected toit a potentiometer 113 which is actually the richness control. Inpractice, potentiometer 113 has a maximum impedance substantially equalto the characteristic impedance of the filter 112a. Since the outputterminal of the filter is not terminated there will be a mismatch at theoutput and a variation of richness control 113.from its characteristicimpedance value causes a mismatch in the input to provide reflections.This provides additional richness in the output signal of loudspeaker61. Additional variation in timbre is achieved by moving the gangedswitch 114.

Although four filters 112a-d are shown in FIG. 7, additional filters maybe used and ganged as desired to produce different sound effects.

Furthermore in addition to the use of filters between amplifier 60 andloudspeaker 61 the same type of filters may be used at the severalinputs to amplifier 60 to individually change the characteristic of theaudio frequency signal output from the balanced modulators 51a-f.

FIG. 8 shows a modification of the stringing arrangement of FIG. 1. Herethe string 116 is coupled directly to two rubber grommets 117a and 1180.Tension may be provided by a cylindrical wedge (not shown) in either ofthe grommets. This construction may be desirable for some applicationsover the spring type construction shown in FIG. 1 where a spring 19 isused.

It is apparent from the foregoing description that many different typesof sound effects which may be produced by the present invention involvethe manipulation of several control knobs. Thus, the present inventioncontemplates the use of matrix cards or similar type devices forpresetting the controls.

Thus, the present invention provides an improved electronic musicalapparatus where the fingerboard of the stringed instrument is actuallysimulated by capacitive-type touch switches allowing greater ease ofplaying. This also provides more accurate frequency output of theinstrument and allows for greater versatility and production ofdifferent types of sound effects from the instrument so modified. Inaddition, the use of strings merely for modifying the amplitude and riseand fall time etc. of the output frequencies again allows a greaterversatility in the sound quality of the instrument.

What we claim is:

1. Electronic musical apparatus comprising, string means adapted forbowing or plucking, a plurality of discrete touch actuated switch meansfor simulating the fingerboard of a stringed musical instrument each ofsaid switch means corresponding to a predetermined audio frequencysignal, oscillator means coupled to said switch means and responsive tothe selective actuation of any one of said switch means for generatingsaid predetermined audio frequency signal corresponding to the switchmeans which has been actuated, transducer means in proximity to saidstring means responsive to the physical displacement of said stringmeans; and modulating means coupled to said oscillator means andtransducer means and responsive to the actuation of said string meansinto vibration concurrently with the actuation of said one switch meansfor modulating said audio frequency signal.

2. Electronic musical apparatus as in claim 1 where said switch meansinclude fixed wire segments for forming virtual capacitors when a humanfinger is placed in proximity with a segment.

3. Electronic musical apparatus as in claim 1 where said switch meansinclude touch actuating means arranged in a straight line correspondingto the various fingering positions of a string in the same physicallocation.

4. Electronic musical apparatus as in claim 1 where said modulatingmeans includes waveshape modifying means for modifying the output ofsaid transducer means.

5. Electronic musical apparatus as in claim 1 including tuning means forsaid oscillating means located in a position corresponding to the tuningmachine of the simulated fingerboard.

6. Electronic musical apparatus as in claim 1 where said plurality ofswitch means include a common radio frequency oscillator for generatingan alternating signal which charges virtual capacitors formed bytouching a predetermined portion of said switch means.

7. Electronic musical apparatus as in claim 1 where said switch meansincludes means coupled to said modulating means and responsive to thedeactivation of said switch means to disable said modulating means.

8. Electronic musical apparatus as in claim 1 where said modulatingmeans includes first and second series coupled balanced modulators saidmodulators providing a logarithmic modulation characteristic.

9. Electronic musical apparatus as in claim 1 where said transducermeans includes first transducer means primarily responsive tolongitudinal mode vibrations of said string means and includes secondtransducer means primarily responsive to transverse mode vibrations ofsaid string means.

10. Electronic musical apparatus as in claim 1 where said transducermeans includes piezoelectric elements mechanically coupled to saidstring means.

11. Electronic musical apparatus as in claim 1 including harmoniccontrol means coupled to said oscillator means for modifying theharmonic content of the audio frequency signal output of said oscillatormeans said harmonic control means including variable integration means.

12. Electronic musical apparatus as in claim 11 Where said variableintegration means comprise a capacitor coupled across a balancedmodulator said modulator including variable gain control means to varythe effective capacitance value of said capacitor.

13. Electronic musical apparatus as in claim 11 where said harmonicmodulator is coupled and responsive to said transducer means.

14. Electronic musical apparatus as in claim 11 where said oscillatormeans produce sawtooth type signals and said variable integration meansattenuate high harmonics of said sawtooth signals.

15. Electronic musical apparatus as in claim 1 including tuning meansfor said oscillator means said tuning means being coupled to a commonjunction and together with means for warying the voltage level of saidjunction to simultaneously vary the frequencies of the audio frequencysignals generated by said oscillator means.

16. Electronic musical apparatus as in claim 15 where said means forvarying said voltage level includes a potentiometer.

17. Electronic musical apparatus as in claim 15 together with foot pedalmeans for controlling said potentiometer.

18. Electronic musical apparatus as in claim 15 where said means forvarying said voltage level includes continuous potentiometer means anddetented potentiometer means and option switch means for selecting oneof said potentiometer means.

19. Electronic musical apparatus as in claim 1 where said oscillatormeans includes at least one unijunction transistor.

20. Electronic musical apparatus comprising, transducer means adaptedfor actuation by a human hand, a plurality of touch actuated switchmeans each including a fixed wire segment for forming a virtualcapacitor with a human finger, each switch means for modulating saidaudiQfrequencJ signal.

21. Electronic musical apparatus as in c arm 0 where said modulatingmeans includes. harmonic control means coupled to said oscillator meansfor modifying the harmonic content of the audio frequency signal outputof said oscillator means said harmonic control means including avariable symmetry chopper driven by said oscillator means for producinga pulse type output signal having a variable pulse width.

22. Electronic musical apparatus as in claim 21 together with controlmeans coupled to said chopper for varying said pulse width.

23. Electronic musical apparatus as in claim 21 where said chopperincludes a saturated differential amplifier.

24. Electronic musical apparatus as in claim 21 where said oscillatormeans produces sawtooth type signals and said chopper clips saidsawtooth signals to produce said pulse type output signal.

25. Electronic musical apparatus as in claim 21 where said chopper iscoupled and responsive to said transducer means for varying the pulsewidth of said output signal.

26. Electronic musical apparatus as in claim 20 where said touchactuated switch means includes means responsive to the skin pressure ofa finger on a wire segment of said switch means for modifying thefrequency of said audio frequency signal of said oscillator means.

27. Electronic musical apparatus as in claim 26 where said touchactuated switch means includes a radio frequency oscillator forgenerating an alternating signal which charges virtual capacitors formedby said finger touching said wire segment said radio frequencyoscillator having an input current proportional to said skin pressuresaid switch means also including control means responsive to said inputcurrent for proportionately modulating said frequency of said audiofrequency signal.

28. Electronic musical apparatus as in claim 20 together with filteringmeans having an input coupled to the modulated output of said modulatingmeans and an output to audio transducer means.

29. Electronic musical apparatus as in claim 28 where said filteringmeans has a frequency filtering characteristic which is variable toprovide control of the timbre of said audio frequency.

30. Electronic musical apparatus as in claim 29 where said filteringmeans includes a plurality of 1r sections comprising an inductor and twocapacitor legs together with switching means for coupling said input andoutput to any two adjacent 1r sections at any one time for providingsaid variation of said filtering characteristic.

31. Electronic musical apparatus as in claim 28 together with impedancemeans coupled to said input of said filtering means having an impedancedifferent from the characteristic impedance of said filtering means.

32. Electronic musical apparatus as in claim 31 where said impedancemeans is variable to provide for control of the richness of said audiofrequency.

1. Electronic musical apparatus comprising, string means adapted forbowing or plucking, a plurality of discrete touch actuated switch meansfor simulating the fingerboard of a stringed musical instrument each ofsaid switch means corresponding to a predetermined audio frequencysignal, oscillator means coupled to said switch means and responsive tothe selective actuation of any one of said switch means for generatingsaid predetermined audio frequency signal corresponding to the switchmeans which has been actuated, transducer means in proximity to saidstring means responsive to the physical displacement of said stringmeans; and modulating means coupled to said oscillator means andtransducer means and responsive to the actuation of said string meansinto vibration concurrently with the actuation of said one switch meansfor modulating said audio frequency signal.
 2. Electronic musicalapparatus as in claim 1 where said switch means include fixed wiresegments for forming virtual capacitors when a human finger is placed inproximity with a segment.
 3. Electronic musical apparatus as in claim 1where said switch means include touch actuating means arranged in astraight line corresponding to the various fingering positions of astring in the same physical location.
 4. Electronic musical apparatus asin claim 1 where said modulating means includes waveshape modifyingmeans for modifying the output of said transducer means.
 5. Electronicmusical apparatus as in claim 1 including tuning means for saidoscillating means located in a position corresponding to the tuningmachine of the simulated fingerboard.
 6. Electronic musical apparatus asin claim 1 where said plurality of switch means include a common radiofrequency oscillator for generating an alternating signal which chargesvirtual capacitors formed by touching a predetermined portion of saidswitch means.
 7. Electronic musical apparatus as in claim 1 where saidswitch means includes means coupled to said modulating means andresponsive to the deactivation of said switch means to disable saidmodulating means.
 8. Electronic musical apparatus as in claim 1 wheresaid modulating means includes first and second series coupled balancedmodulators said modulators providing a logarithmic modulationcharacteristic.
 9. Electronic musical apparatus as in claim 1 where saidtransducer means includes first transducer means primarily responsive tolongitudinal mode vibrations of said string means and includes secondtrAnsducer means primarily responsive to transverse mode vibrations ofsaid string means.
 10. Electronic musical apparatus as in claim 1 wheresaid transducer means includes piezoelectric elements mechanicallycoupled to said string means.
 11. Electronic musical apparatus as inclaim 1 including harmonic control means coupled to said oscillatormeans for modifying the harmonic content of the audio frequency signaloutput of said oscillator means said harmonic control means includingvariable integration means.
 12. Electronic musical apparatus as in claim11 where said variable integration means comprise a capacitor coupledacross a balanced modulator said modulator including variable gaincontrol means to vary the effective capacitance value of said capacitor.13. Electronic musical apparatus as in claim 11 where said harmonicmodulator is coupled and responsive to said transducer means. 14.Electronic musical apparatus as in claim 11 where said oscillator meansproduce sawtooth type signals and said variable integration meansattenuate high harmonics of said sawtooth signals.
 15. Electronicmusical apparatus as in claim 1 including tuning means for saidoscillator means said tuning means being coupled to a common junctionand together with means for warying the voltage level of said junctionto simultaneously vary the frequencies of the audio frequency signalsgenerated by said oscillator means.
 16. Electronic musical apparatus asin claim 15 where said means for varying said voltage level includes apotentiometer.
 17. Electronic musical apparatus as in claim 15 togetherwith foot pedal means for controlling said potentiometer.
 18. Electronicmusical apparatus as in claim 15 where said means for varying saidvoltage level includes continuous potentiometer means and detentedpotentiometer means and option switch means for selecting one of saidpotentiometer means.
 19. Electronic musical apparatus as in claim 1where said oscillator means includes at least one unijunctiontransistor.
 20. Electronic musical apparatus comprising, transducermeans adapted for actuation by a human hand, a plurality of touchactuated switch means each including a fixed wire segment for forming avirtual capacitor with a human finger, each of said switch meanscorresponding to a predetermined audio frequency signal, oscillatormeans coupled to said switch means and responsive to the selectiveactuation of any one of said switch means for generating an audiofrequency signal corresponding to the switch means which has beenactuated; and modulating means coupled to said oscillator means andtransducer means and responsive to the actuation of said transducermeans concurrently with the actuation of said one switch means formodulating said audio frequency signal.
 21. Electronic musical apparatusas in claim 20 where said modulating means includes harmonic controlmeans coupled to said oscillator means for modifying the harmoniccontent of the audio frequency signal output of said oscillator meanssaid harmonic control means including a variable symmetry chopper drivenby said oscillator means for producing a pulse type output signal havinga variable pulse width.
 22. Electronic musical apparatus as in claim 21together with control means coupled to said chopper for varying saidpulse width.
 23. Electronic musical apparatus as in claim 21 where saidchopper includes a saturated differential amplifier.
 24. Electronicmusical apparatus as in claim 21 where said oscillator means producessawtooth type signals and said chopper clips said sawtooth signals toproduce said pulse type output signal.
 25. Electronic musical apparatusas in claim 21 where said chopper is coupled and responsive to saidtransducer means for varying the pulse width of said output signal. 26.Electronic musical apparatus as in claim 20 where said touch actuatedswitch means includes means responsive to the skin pressure of a fingeron a wire segment of said switch means for modifying tHe frequency ofsaid audio frequency signal of said oscillator means.
 27. Electronicmusical apparatus as in claim 26 where said touch actuated switch meansincludes a radio frequency oscillator for generating an alternatingsignal which charges virtual capacitors formed by said finger touchingsaid wire segment said radio frequency oscillator having an inputcurrent proportional to said skin pressure said switch means alsoincluding control means responsive to said input current forproportionately modulating said frequency of said audio frequencysignal.
 28. Electronic musical apparatus as in claim 20 together withfiltering means having an input coupled to the modulated output of saidmodulating means and an output to audio transducer means.
 29. Electronicmusical apparatus as in claim 28 where said filtering means has afrequency filtering characteristic which is variable to provide controlof the timbre of said audio frequency.
 30. Electronic musical apparatusas in claim 29 where said filtering means includes a plurality of pisections comprising an inductor and two capacitor legs together withswitching means for coupling said input and output to any two adjacentpi sections at any one time for providing said variation of saidfiltering characteristic.
 31. Electronic musical apparatus as in claim28 together with impedance means coupled to said input of said filteringmeans having an impedance different from the characteristic impedance ofsaid filtering means.
 32. Electronic musical apparatus as in claim 31where said impedance means is variable to provide for control of therichness of said audio frequency.